1. Field of the Invention
The present invention relates to a magnetic bearing device, a magnetic bearing control device for controlling a rotary body by using a magnetic bearing, and a vacuum pump and, more particularly, to a magnetic bearing device and a magnetic bearing control device used in a main spindle of a machine tool, a vacuum pump or the like.
2. Description of the Related Art
With such a magnetic bearing device, it is possible to levitate a rotary body and perform super high speed rotation thereof in a contactless manner and an oilless manner, to use the device in the vicinity of clean rooms and to dispense with routine maintenance such as changing oil or bearings. For this reason, the magnetic bearing device is widely used in a centrifugal atomizer for producing metal powder, metal pipe machining, a main spindle of a machine tool such as a cylinder grinder, and a vacuum pump.
FIG. 5 shows a general structure of the conventional magnetic bearing device.
As shown in FIG. 5, the magnetic bearing device is provided with a magnetic bearing body A and a control device B which are connected with each other through cables.
The magnetic bearing body A is basically composed of a rotary shaft 81, a motor 82 provided around the rotary shaft 81 for rotating the rotary shaft 81, and a magnetic bearing 83 for magnetically floating and supporting both ends of the rotary shaft 81.
The control device B is basically composed of a motor drive circuit 84, amplifiers 91 and 93 and PID controllers 90 and 92.
Any type of appropriate motor, such as a brushless DC motor or a high frequency motor, may be used as the motor 82. The motor drive circuit 84 drives a motor drive coil 85 fixed around the rotary shaft 81 so that the rotary shaft 81 may be rotated.
The magnetic bearing 83 is provided with two pairs of electromagnets 86 that are arranged to face each other with respect to the rotary shaft 81 (in which both pairs are perpendicular to each other and this will hereinafter be the same), two pairs of displacement sensors 89 arranged to face each other in the vicinity thereof, two pairs of electromagnets 87 that are arranged to face each other and two pairs of displacement sensors 89 arranged to face each other in the vicinity thereof.
Each displacement sensor 88, 89 detects a radial displacement of the rotary shaft 81 to feed this detected displacement to the control device B.
When the detected displacements by the displacement sensors 88 and 89 are fed to the control device B, the PID controllers 90 and 92 compare the detected displacements with target values, the control device B provides the amplifiers 91 and 93 (electromagnet drive circuits) with such a signal that both are identical. Then, magnetic forces of the corresponding electromagnets 86 and 87 are controlled so that the rotary shaft 81 is displaced to the target position by the amplifiers 91 and 93. As a result, the rotary shaft 81 may be magnetically supported in a contactless condition.
In such a conventional magnetic bearing device, since an error is generated at a mechanical central position and at an electric central position of the rotary body including the rotary shaft 81, their adjustments are required to correct each magnetic bearing body A for every unit. Also, sizes of the magnetic bearing bodies A and various characteristics such as a current value, standard value or the like for magnetically floating and controlling the rotary body are different depending upon the model type (product specification). Therefore, since the floating position is changed depending upon the difference, it is necessary to make setup for every model type.
Accordingly, the parameters are changed for the control of the control device B for every unit of the magnetic bearing body A to be connected. This should be done by the specialists for adjustment or setup.
Also, in the conventional magnetic bearing device, in the case where the magnetic bearing body A is replaced by another model, it is requisite to change the parameters of the control device B. Therefore, there is no special countermeasure for the case where the machine is driven without any change.
Furthermore, the conventional device does not cope with the case where the values of the parameters set in the control device B become abnormal due to electric or mechanical faults or the like.
Thus, when the magnetic bearing body A is controlled with the different parameters, the magnetic bearing body A can not exhibit the sufficient ability as the magnetic bearing or causes a breakdown of the device.
Accordingly, the present invention has been made in order to overcome the above-noted problems inherent in the conventional magnetic bearing device, and a primary object of the present invention is to provide a magnetic bearing device having means for enabling a control device to check the model of the magnetic bearing to be connected thereto.
Also, a second object of the invention is to provide a magnetic bearing control device that may automatically perform confirmation and adjustment of parameters for controlling the magnetic bearing body.
In order to attain the primary object, according to the present invention, there is provided a magnetic bearing device for magnetically floating a rotary shaft to hold the rotary shaft in a contactless manner, comprising: a model type identifying means for identifying a model type; a first memory means for storing various characteristic values corresponding to the model type; and a connecting means for accessing the model type identifying means and the first memory means from the outside.
In the magnetic bearing device according to the invention, the model type identifying means comprises a resistor having a resistance value determined corresponding to the model type, and the memory means comprises a rewritable memory means.
In order to attain the second object, according to the present invention, there is provided a magnetic bearing control device for performing a magnetically floating control for a magnetic bearing device magnetically floating a rotary shaft to hold the rotary shaft in a contactless manner, comprising: a second memory means which is rewritable for storing a model type and various characteristic values of a magnetic bearing to be connected; an obtaining means for obtaining the model type and various characteristic values of the magnetic bearing device through a connecting means of the magnetic bearing device; a renewal means for renewing a content of the second memory means to a content of a first memory means if the model type and various characteristic values obtained by the obtaining means and the model type and various characteristic values stored in the second memory means are different from each other; and a controlling section for performing magnetically floating control for the magnetic bearing device to be connected in accordance with the characteristic values stored in the second memory means.
In the magnetic bearing device according to the invention, there is further provided a judgment means for judging whether or not contents of the first memory means and the second memory means are normal, and the renewal means renews the content of the second memory means to the content of the first memory means if it is judged by the judgment means such that contents of the first memory means and the second memory means are normal.
In order to attain the second object, according to the present invention, there is provided a magnetic bearing control device for performing a magnetically floating control for a magnetic bearing device magnetically floating a rotary shaft to hold the rotary shaft in a contactless manner, comprising: a second memory means which is rewritable for storing a model type and various characteristic values of a magnetic bearing to be connected; an obtaining means for obtaining the model type and various characteristic values of the magnetic bearing device through a connecting means of the magnetic bearing device; a judgment means for judging whether or not contents of the first memory means and the second memory means are normal; a renewal means, if the judgment means judges such that one of contents of the first memory means and the second memory means is abnormal, for renewing the content of one of the first and second memory means to the content of the other that has been judged to be normal; and a controlling section for performing magnetically floating control for the magnetic bearing device to be connected in accordance with the various characteristic values stored in the second memory means.
In order to attain the second object, according to the present invention, there is provided a magnetic bearing control device for performing a magnetically floating control for a magnetic bearing device for magnetically floating a rotary shaft to hold the rotary shaft in a contactless manner, comprising: a second memory means which is rewritable for storing a model type and various characteristic values of a magnetic bearing to be connected; an obtaining means for obtaining the model type and various characteristic values of the magnetic bearing device through a connecting means of the magnetic bearing device; a judgment means for judging whether or not contents of the first memory means and the second memory means are normal; a third memory means for storing various characteristic values corresponding to a plural kinds of model types; a renewal means, if the judgment means judges that contents of the first memory means and the second memory means are abnormal, for reading the various characteristic values corresponding to the model type obtained by the obtaining means from the third memory means and renewing the contents of the first and second memory means; and a controlling section for performing magnetically floating control for the magnetic bearing device to be connected in accordance with the various characteristic values stored in the second memory means.